A new modification of the single nucleotide polymorphism (SNP) analysis (DSNP, duplex-specific nuclease preference) method using the duplex-specific nuclease from the king crab was proposed. The method was used to study SNPs in the following human genes: kRAS, nRAS, hRAS, and p53, the genes of blood coagulation factor V, methyltetrahydrofolate reductase, prothrombin, and apolipoprotein E and a deletion in the BRCA1 gene. DSNP was shown to be useful for the estimation of the mutant allele content in DNA samples. A system for the simultaneous identification of several adjacent single-nucleotide polymorphisms in the kRAS gene was proposed. The approaches could be used to develop test systems for the detection of SNPs in human genes.